CVE-2021-21387

Partial secret key disclosure, improper safety number calculation, & inadequate encryption strength

HIGH
7.5
CVSS Score
Published: March 19, 2021 at 03:25 PM UTC
Updated: June 17, 2026 at 03:35 AM UTC
2 products affected across 2 vendorsWrongthinkWrongthink

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Severity
HIGH7.5
Exploit prediction
EPSS 0.4%

Description

Wrongthink peer-to-peer, end-to-end encrypted messenger with PeerJS and Axolotl ratchet. In wrongthink from version 2.0.0 and before 2.3.0 there was a set of vulnerabilities causing inadequate encryption strength. Part of the secret identity key was disclosed by the fingerprint used for connection. Additionally, the safety number was improperly calculated. It was computed using part of one of the public identity keys instead of being derived from both public identity keys. This caused issues in computing safety numbers which would potentially be exploitable in the real world. Additionally there was inadequate encryption strength due to use of 1024-bit DSA keys. These issues are all fixed in version 2.3.0.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2.0.0 ≤ v < 2.3.0
Affected range stops below 2.3.0, so it looks safe — our inference, not a vendor statement
v < 2.2.0
Affected range stops below 2.2.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-319CWE-326CWE-358

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